Well it all depends. iPod would be my choice, because I bought an iPad and it was great at first, but it started becoming a hassle to have to carry it around everywhere; since it's not that small. I would say buy an iPod if you're going to use it more for music than gaming.
it depends what you're gonna use it for.
do you mainly want to listen to music? get an iPod touch, they have up to 64gb capacity.
do you mainly want to use apps/go online? an iPad would probably be better.